1. Field of the Invention
This invention relates to a semiconductor device and manufacturing method thereof, specifically to a semiconductor device encapsulated in a package having roughly the same outside dimensions as a semiconductor die packaged in it and a manufacturing method thereof.
2. Description of the Related Art
A CSP (Chip Size Package) has received attention in recent years as a new packaging technology. The CSP means a small package having about the same outside dimensions as those of a semiconductor die packaged in it. A BGA type semiconductor device has been known as a kind of CSP. A plurality of ball-shaped conductive terminals made of metal such as solder is arrayed in a grid pattern on one principal surface of a package of the BGA type semiconductor device and is electrically connected with the semiconductor die mounted on the other side of the package.
When the BGA type semiconductor device is mounted on electronic equipment, the semiconductor die is electrically connected with an external circuit on a printed circuit board by compression bonding of the conductive terminals to wiring patterns on the printed circuit board.
Such a BGA type semiconductor device has advantages in providing a large number of conductive terminals and in reducing size over other CSP type semiconductor devices such as an SOP (Small Outline Package) and a QFP (Quad Flat Package), which have lead pins protruding from their sides. The BGA type semiconductor device is used as an image sensor chip for a digital camera incorporated into a mobile telephone, for example.
FIGS. 13A and 13B show outline structure of a conventional BGA type semiconductor device. FIG. 13A is an oblique perspective figure showing a top side of the BGA type semiconductor device. And FIG. 13B is an oblique perspective figure showing a back side of the BGA type semiconductor device.
A semiconductor die 101 is sealed between a first glass substrate 104a and a second glass substrate 104b through resins 105a and 105b in the BGA type semiconductor device 100. A plurality of ball-shaped conductive terminals (hereafter referred to as conductive terminals) 111 is arrayed in a grid pattern on a principal surface of the second glass substrate 104b, that is, on a back surface of the BGA type semiconductor device 100. The conductive terminals 111 are connected to the semiconductor die 101 through a plurality of second wirings 109. The plurality of second wirings 109 is connected with aluminum first wirings pulled out from inside of the semiconductor die 101, making each of the conductive terminals 111 electrically connected with the semiconductor die 101.
More detailed explanation on a cross-sectional structure of the BGA type semiconductor device 100 is given hereafter referring to FIG. 14. FIG. 14 shows a cross-sectional view of the BGA type semiconductor devices 100 divided along dicing lines into individual dice.
The first wiring 103 is provided on an insulation film 102 on a top surface of the semiconductor die 101. The semiconductor die 101 is bonded to the first glass substrate 104a with the resin 105a. A back surface of the semiconductor die 101 is bonded to the second glass substrate 104b with the resin 105b. One end of the first wiring 103 is connected to the second wiring 109. The second wiring 109 extends from the end of the first wiring 103 to a surface of the second glass substrate 104b. The ball-shaped conductive terminal 111 is formed on the second wiring 109 extending onto the second glass substrate 104b. 
The semiconductor device described above has disadvantages of increased thickness and higher manufacturing cost, since it uses two glass substrates. So, a method to bond the glass substrate only to the top surface of the semiconductor die, on which the first wiring is formed, has been considered. In this case, the bottom surface of the device is made of the semiconductor substrate which is easier to process by etching compared with the glass substrate. Taking this advantage, the first wiring is exposed by etching the semiconductor substrate and the insulation film in the dicing line region in order for the first wiring to be connected with the second wiring. As a result, a contact area between the first wiring and the second wiring is increased, compared with the conventional method using two glass substrates. After forming the second wirings, a protection film and the conductive terminals, the semiconductor substrate is finally separated into individual semiconductor dice by cutting the glass substrate.
The insulation film formed on the semiconductor substrate is left exposed in the dicing line region after the first wiring is exposed. At that time, only the insulation film, the resin and the glass substrate exist in the dicing line region. Considering thickness of each component, all of the semiconductor dice are supported practically only with the glass substrate. Furthermore, considerable warping is caused in the glass substrate, because of the difference in thermal expansion coefficients between the semiconductor substrate and the glass substrate. Therefore, weights of the semiconductor dice and others bonded to the glass substrate are imposed on the glass substrate during handling in the manufacturing process. In some cases, this may cause separation 204 between the semiconductor die and the glass substrate (not shown) in peripheral regions of the semiconductor dice and cracks 205 in the glass substrate 202, as shown in FIG. 11. Thus, the yield and reliability of the semiconductor devices have been reduced.